Collaborative Research: Multiscale Study of Active Cellular Matter: Simulation, Modeling, and Analysis

活性细胞物质是由悬浮的细胞骨架细丝和分子马达的混合物制成的新型合成活性流体的基础。通过消耗化学燃料，分子发动机（例如，驱动蛋白）可以结合并在生物丝之间产生主动移动的交联（例如，微管）驱动它们的相对运动，这导致通过流体动力学耦合在细丝/马达混合物中的大规模集体运动。由少量成分组成的合成活性悬浮液揭示了活细胞中组装和组织的高阶方面是如何构建的。这些系统也对我们理解、设计和分析材料提出了新的挑战，并有可能提供有价值的新技术，如自主移动和自我修复材料。在这项工作中，研究人员通过多尺度方法和紧密耦合的建模，分析和模拟来研究由微管和分子马达组成的活性细胞物质。该项目旨在了解经历动态不稳定性的刚性/柔性生物丝束内应力产生的基本相互作用，以及大规模集体运动中的非线性动力学和分层模式形成。该项目还将预测关键材料特性，包括其相干结构，局部异质性，时间和长度尺度以及材料流变学。为了解决不同长度和时间尺度上的物理问题，将开发和集成几种方法：（1）微管-马达相互作用将使用动力学Monte Carlo方法模拟;（2）各种形状物体之间的流体动力学相互作用将使用非局部细长体/边界积分方法以及快速求和方法模拟;（3）采用伪谱方法，通过一个连续的主动液晶型模型来模拟集体运动。

Active cellular matter is the basis of novel synthetic active fluids made of mixtures of suspended cytoskeletal filaments and molecular motors. By consuming chemical fuel, the molecular motors (e.g., kinesins) can bind to and create actively moving crosslinks between the biofilaments (e.g., microtubules) to drive their relative motion, which leads to large-scale collective motions in the filament/motor mixture through hydrodynamic coupling. Synthetic active suspensions made of small numbers of components reveal how higher-order aspects of assembly and organization are built in living cells. These systems also present new challenges to our understanding, design, and analysis of materials, and have the potential to provide valuable new technologies such as autonomously moving and self-healing materials.In this work, the investigators study active cellular matter composed of microtubules and molecular motors through multiscale methods, and tightly coupled modeling, analysis, and simulation. The project aims to understand the fundamental interactions underlying stress generation within bundles of rigid/flexible biofilaments that undergo dynamic instability, as well as the nonlinear dynamics and hierarchical pattern formation in large-scale collective motions. The project will also predict key material properties including its coherent structures, local heterogeneity, time- and length-scales, and material rheology. To resolve the physics at different length- and time-scales, several methods will be developed and integrated: (1) microtubule-motor interactions will be simulated using a kinetic Monte Carlo method; (2) the hydrodynamic interactions between objects of various shapes will be modeled using a nonlocal slender body/boundary integral method, together with fast summation methods; (3) a pseudo-spectral method will be implemented to simulate the collective motion through a continuous active liquid-crystal type model.